Studies will be carried out to determine the nature of the independent, vasopressin-sensitive pathways for water and solute movement across the luminal membrane of the toad bladder and renal tubular cell. A variety of inhibitory agents which are specific for two of the major transport pathways (amides and water) will be used. These agents include chromate and permanganate, which inhibit amide transport, and the anesthetic agents methoxyflurane and halothane. Studies will be carried out in other epithelia as well, including the gastrointestinal tract, to see if these selective pathways are present.